Mechanism of bromide ion oxidation on Pt electrode in CH2Cl2

An oscillation system of Belousov-Zhabotinskii type with aldehyde as substrate is described for the first time. Oscillations of the concentration of Mn(III) ions can be followed spectrophotometrically or potentiometrically with a Pt electrode in a relatively narrow concentration range of the substrate. In contrast to the analogous reaction with malonic acid, no oscillations of the concentration of Br- ions were detected by a bromide ion selective electrode. This together with the fact that the concentration of Mn(III) ions oscillates even at relatively high bromine concentrations suggests that oscillations of the concentration of the redox catalyst Mn(II)/Mn(III) are probably controlled by organic radicals rather than by Br- ions.

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Coordination state of cobalt(II) ions in solution and on a sulphonated organic polymer

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19792330 ◽

1979 ◽

Vol 44 (8) ◽

pp. 2330-2337 ◽

Cited By ~ 1

Author(s):

Jindřiška Maternová ◽

Anastas A. Andreev ◽

Dimitrii M. Shopov ◽

Karel Setínek

Keyword(s):

Acetic Acid ◽

Coordination Sphere ◽

Glacial Acetic Acid ◽

Organic Polymer ◽

Octahedral Complex ◽

Coordination State ◽

Tetrahedral Symmetry ◽

Liquid Acid ◽

Homogeneous Phase ◽

Bromide Ion

It was found spectroscopically that cobalt(II) acetate dissolved in glacial acetic acid forms the octahedral complex [Co(OAc)2(HOAc)4] which in the presence of bromide ions gives the octahedral [Co(OAc)Br(HOAc)4] and tetrahedral bromo(acetate)cobalt(II) complexes with the higher number of Br- ions. When attached to an organic polymer cobalt(II) ions are bonded in the form of octahedral [Co(H2O)6]2+ cations which form with acetic acid similar complexes as in homogeneous phase and are able to coordinate one bromide ion. Drying the copolymer possessing octahedral hexaaquocobalt(II) cations leads to tetrahedral aquocomplexes which are solvated by gaseous acetic acid and converted into the acetate complexes with the liquid acid. The latter contain the acid in the inner coordination sphere and have tetrahedral symmetry.

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Effects of Doping on the Electrochemical and Electrical Properties of Poly(2,5-di(2-thienyl)pyrrole)

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19991357 ◽

1999 ◽

Vol 64 (8) ◽

pp. 1357-1368 ◽

Cited By ~ 7

Author(s):

Enric Brillas ◽

José Carrasco ◽

Ramon Oliver ◽

Francesc Estrany ◽

Víctor Ruiz

Keyword(s):

Mass Spectrometry ◽

Fast Atom Bombardment ◽

Oxidation Potential ◽

Ethanolic Solution ◽

Pt Electrode ◽

Reversible Process ◽

Oxidation Potentials ◽

Lower Productivity ◽

Polymeric Chains ◽

Linear Molecules

The electropolymerization of 2,5-di(2-(thienyl)pyrrole) (SNS) on a Pt electrode from ethanolic solution with LiClO4 or LiCl as electrolyte has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). In both media, a quasi-reversible process has been indicated by CV, reversing the scan at low oxidation potentials. Under these conditions, reducible positive charges formed in both oxidized polymers are compensated by the entrance of anions from solution. Elemental analysis reveals that polymers generated at a low oxidation potential by CA contain a 21.03% (w/w) of ClO4- or a 9.56% (w/w) of Cl-. The poly(SNS) doped with Cl- presents higher proportion of reducible positive charges, higher polymerization charge and lower productivity. A much higher electrical conductivity, however, has been found for the poly(SNS) doped with ClO4-. Both polymers are soluble in DMSO, acetone and methanol. The dimer, trimer, tetramer and pentamer have been detected as soluble and neutral linear oligomers by mass spectrometry-fast atom bombardment. The analysis of polymers by infrared spectroscopy confirms the predominant formation of linear molecules with α-α linkages between monomeric units. A condensation mechanism involving one-electron oxidation of all electrogenerated linear and neutral polymeric chains is proposed to explain the SNS electropolymerization.

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Redox Potential - (Electronic) Structure Relationships in 18- and 17-Electron Mononitrile (or Monocarbonyl) Diphosphine Complexes of Re and Fe

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20010139 ◽

2001 ◽

Vol 66 (1) ◽

pp. 139-154 ◽

Cited By ~ 11

Author(s):

M. Fátima C. Guedes Da Silva ◽

Luísa M. D. R. S. Martins ◽

João J. R. Fraústo Da Silva ◽

Armando J. L. Pombeiro

Keyword(s):

Cyclic Voltammetry ◽

Electronic Structure ◽

Binding Sites ◽

Closed Shell ◽

Carbonyl Complexes ◽

Metal Centre ◽

Pt Electrode ◽

Metal Site ◽

Oxidation Potentials ◽

First Time

The organonitrile or carbonyl complexes cis-[ReCl(RCN)(dppe)2] (1) (R = 4-Et2NC6H4 (1a), 4-MeOC6H4 (1b), 4-MeC6H4 (1c), C6H5 (1d), 4-FC6H4 (1e), 4-ClC6H4 (1f), 4-O2NC6H4 (1g), 4-ClC6H4CH2 (1h), t-Bu (1i); dppe = Ph2PCH2CH2PPh2), or cis-[ReCl(CO)(dppe)2] (2), as well as trans-[FeBr(RCN)(depe)2]BF4 (3) (R = 4-MeOC6H4 (3a), 4-MeC6H4 (3b), C6H5 (3c), 4-FC6H4 (3d), 4-O2NC6H4 (3e), Me (3f), Et (3g), 4-MeOC6H4CH2 (3h); depe = Et2PCH2CH2PEt2), novel trans-[FeBr(CO)(depe)2]BF4 (4) and trans-[FeBr2(depe)2] (5) undergo, as revealed by cyclic voltammetry at a Pt-electrode and in aprotic non-aqueous medium, two consecutive reversible or partly reversible one-electron oxidations assigned as ReI → ReII → ReIII or FeII → FeIII → FeIV. The corresponding values of the oxidation potentials IE1/2ox and IIE1/2ox (waves I and II, respectively) correlate with the Pickett's and Lever's electrochemical ligand and metal site parameters. This allows to estimate these parameters for the various nitrile ligands, depe and binding sites (for the first time for a FeIII/IV couple). The electrochemical ligand parameter show dependence on the "electron-richness" of the metal centre. The values of IE1/2ox for the ReI complexes provide some supporting for a curved overall relationship with the sum of Lever's electrochemical ligand parameter. The Pickett parametrization for closed-shell complexes is extended now also to 17-electron complexes, i.e. with the 15-electron ReII and FeIII centres in cis-{[ReCl(dppe)2]}+ and trans-{FeBr(depe)2}2+, respectively.

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Mixed Lithium and Sodium Ion Aprotic DMSO Electrolytes for Oxygen Reduction on Au and Pt Studied by DEMS and RRDE

Electrocatalysis ◽

10.1007/s12678-021-00669-4 ◽

2021 ◽

Author(s):

M. Hegemann ◽

P. P. Bawol ◽

A. Köllisch-Mirbach ◽

H. Baltruschat

Keyword(s):

Oxygen Reduction ◽

Product Distribution ◽

Reduction Reaction ◽

Mixed Electrolytes ◽

Peroxide Formation ◽

Pt Electrode ◽

Rate Determining Step ◽

Differential Electrochemical Mass Spectrometry ◽

Redox Couples ◽

Pt Electrodes

AbstractIn order to advance the development of metal-air batteries and solve possible problems, it is necessary to gain a fundamental understanding of the underlying reaction mechanisms. In this study we investigate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER, from species formed during ORR) in Na+ containing dimethyl sulfoxide (DMSO) on poly and single crystalline Pt and Au electrodes. Using a rotating ring disk electrode (RRDE) generator collector setup and additional differential electrochemical mass spectrometry (DEMS), we investigate the ORR mechanism and product distribution. We found that the formation of adsorbed Na2O2, which inhibits further oxygen reduction, is kinetically favored on Pt overadsorption on Au. Peroxide formation occurs to a smaller extent on the single crystal electrodes of Pt than on the polycrystalline surface. Utilizing two different approaches, we were able to calculate the heterogeneous rate constants of the O2/O2− redox couple on Pt and Au and found a higher rate for Pt electrodes compared to Au. We will show that on both electrodes the first electron transfer (formation of superoxide) is the rate-determining step in the reaction mechanism. Small amounts of added Li+ in the electrolyte reduce the reversibility of the O2/O2− redox couples due to faster and more efficient blocking of the electrode by peroxide. Another effect is the positive potential shift of the peroxide formation on both electrodes. The reaction rate of the peroxide formation on the Au electrode increases when increasing the Li+ content in the electrolyte, whereas it remains unaffected on the Pt electrode. However, we can show that the mixed electrolytes promote the activity of peroxide oxidation on the Pt electrode compared to a pure Li+ electrolyte. Overall, we found that the addition of Li+ leads to a Li+-dominated mechanism (ORR onset and product distribution) as soon as the Li+ concentration exceeds the oxygen concentration. Graphical abstract

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Immobilization of Pt nanoparticles on hydrolyzed polyacrylonitrile-based nanofiber paper

Scientific Reports ◽

10.1038/s41598-021-90536-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Soon Yeol Kwon ◽

EunJu Ra ◽

Dong Geon Jung ◽

Seong Ho Kong

Keyword(s):

Particle Size ◽

Uniform Distribution ◽

Pt Nanoparticles ◽

Electrochemical Activity ◽

Aggregate Formation ◽

Free Standing ◽

Pt Electrode ◽

Catalytic Current ◽

Nucleation Sites ◽

Hydrolysis Of

AbstractThe electrochemical activity of catalysts strongly depends on the uniform distribution of monodisperse Pt nanoparticles without aggregates. Here, we propose a new hydrolysis-assisted smearing method for Pt loading on a free-standing paper-type electrode. Polyacrylonitrile (PAN)-based nanofiber paper was used as the electrode, and it acted as a Pt support. Hydrolysis of the electrode tripled the number of active nucleation sites for Pt adsorption on the PAN nanofibers, thereby significantly enhancing the wettability of the nanofibers. This facilitated the uniform distribution of Pt nanoparticles without aggregate formation up to 40 wt% (about 0.8 mg/cm2) with a particle size of about 3 nm. The catalytic current of the hydrolyzed Pt electrode in CH3OH/H2SO4 solution exceeded 213 mA/cm2 Pt mg, which was considerably greater than the current was 148 mA/cm2 Pt mg for an unhydrolyzed electrode.

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